Deep Delves?

[distressedjazz]

Can anybody help me work out how to do a deep delve? 
I've read you need to reach level 100 in a faction assault event then participate in a level 100 or over delve but you must change to deep delve, however I've tried this the past few events and haven't found the option to make it a deep delve. 

[acasser]

The trophy is not tied to the Faction Assault events.  It's tied to your daily delving attempts if you choose to pursue those.

 

You have the option to spend two daily "delve" sigils (instead of the usual one) to make your attempt at a particular delve a deep delve, but only if the level of the delve you're attacking is 100+ and it's one of the factions where a deep delve has been released (All Seeing Eye, Crypt Keepers, Hall of Guardians, Sea of Sorrow, Primal Rift are the only five delves with deep delves at present; the others are scheduled to be gradually introduced as time goes by).  So it's not an option that will be made available to you if you simply do delves at low(er) levels while grinding for resources like Chaos Shards.

[distressedjazz]

This helps me tremendously. I was aware that you needed a level 100+ delve and I've used faction assault events to get them there. Then couldn't find the option. I wasn't aware they have only released deep delve options for five specific factions so far. Thank you